Multiturn Extraction: Performance Analysis of Old and New Approaches

Super Proton Synchrotron. The present approach is based on beam slicing via an electrostatic septum. However, recently a novel technique was proposed. By using nonlinear magnetic elements, stable islands can be generated in the transverse phase space. Furthermore, if the linear tune is varied slowly, it is possible to trap the charged particles inside the stable islands so that the beam is split into different beamlets ready for extraction. In this paper, both techniques are discussed in details with special emphasis on their robustness and the phase space matching of the extracted beam

Computation of betatron mismatch and emmitance blow-up for multi-turn extraction

The present version of the five-turn Continuous Transfer extraction at PS machine is based on beam slicing by means of an electrostatic septum. Recently, a novel approach has been proposed, where the beam is split into five beamlets by means of stable islands, created by sextupoles and octupoles, together with a proper tune variation. In this paper, the two approaches are compared by considering their properties in terms of equivalent optical parameters, beam emittance, and emittance after filamentation in the receiving machine (SPS) for the various slices. Analytic expressions of the relevant optical and beam parameters are derived for the present version of the Continuous Transfer, while the same quantities are estimated in the case of the novel approach via numerical simulations. Finally, the robustness of the approach based on adiabatic capture in transverse phase space is discussed with particular emphasis on tune ripple effects and variation of nonlinear elements strength

Novel Method for Multi-turn Extraction: trapping charged Particles in Islands of Phase Space

A novel method for multi-turn extraction from a circular particle accelerator is presented. It is based on trapping particles into islands of phase space generated by nonlinear resonances. By appropriate use of nonlinear elements (sextupoles, octupoles), stable islands can be created at small amplitude in phase space. By varying the linear tune, it is shown how particles can be trapped inside these islands. The particles can then be coherently transported towards higher amplitudes for extraction. Results of numerical simulations are presented and discussed in detail

Non-linear correction schemes for the Phase 1 LHC Insertion Region Upgrade and Dynamic Aperture studies

The Phase 1 LHC Interaction Region (IR) upgrade aims at increasing the machine luminosity essentially by reducing the beam size at the Interaction Point (IP). This requires a total redesign of the full IR. A large set of options have been proposed with conceptually different designs. This paper reports on a general approach for the compensation of the multipolar errors of the IR magnets in the design phase. The goal is to use the same correction approach for the different designs. The correction algorithm is based on the minimization of the differences between the IR transfer map with errors and the design IR transfer map. Its performance is tested using the dynamic aperture as figure of merit. The relation between map coefficients and resonance terms is also given as a way to target particular resonances by selecting the right map coefficients. The dynamic aperture is studied versus magnet aperture using recently established relations between magnetic errors and magnet aperture

Correction of Multipolar Field Errors in Insertion Regions for the Phase 1 LHC Upgrade and Dynamic Aperture

The Phase 1 upgrade of the LHC interaction regions aims at increasing the machine luminosity by reducing the beam size at the interaction point. This requires an in-depth review of the full insertion region layout and a large set of options have been proposed with conceptually different designs. This paper reports on a general approach for the compensation of the non-linear eld errors of the insertion region magnets by means of dedicated correctors. The goal is to use the same correction approach for all the different layouts. The correction algorithm is based on the computation of the high orders of the polynomial transfer map using MAD-X and Polymorphic Tracking Code, while the actual performance of the method is estimated by computing the dynamic aperture of the layouts under study

The Proton Beams for the New Time-of-Flight Neutron Facility at the CERN-PS

The experimental determination of neutron cross sections in fission and capture reactions as a function of the neutron energy is of primary importance in nuclear physics. Recent developments at CERN and elsewhere have shown that many fields of research and development, such as the design of Accelerator-Driven Systems (ADS) for nuclear waste incineration, nuclear astrophysics, fundamental nuclear physics, dosimetry for radiological protection and therapy, would benefit from a better knowledge of neutron cross sections. A neutron facility at the CERN-PS has been proposed with the aim of carrying out a systematic and high resolution study of neutron cross sections through Time-Of-Flight (n-TOF) measurement. The facility requires a high intensity proton beam (about 0.7x1013 particles/bunch) distributed in a short bunch (about 25 ns total length) to produce the neutrons by means of a spallation process in a lead target. To achieve these characteristics, a number of complex beam gymnastics have to be performed. All the beam manipulations are presented in this paper as well as some beam dynamics issues encountered during the setting up. The details of the new transfer line used to deliver the beam onto the target are also described

Test of the Sorting Methods at the CERN-SPS

An external study of the effectiveness of the sorting strategies on the CERN Super-Proton-Synchrotron is proposed. The eight strong extraction sextupoles used for diffusion experiments can be independently powered to simulate random errors. Numerical computations show that a significant spread in the dynamic aperture can be obtained. A sorting strategy based on analytical quality factors allows a considerable improvement on the beam stability. A complete analysis of the possible permutations shows that the good configurations are rather abundant. The effectiveness of the ordering procedure is verified for long-term six-dimensional motion and different working points. Situations are presented where the beneficial effect of the sorting is expected to be large and well measurable in realistic conditions of operation